A filter element which is inserted into a housing of a ventilation system of an automobile is known from DE 10 2005 048 841 B3. With this filter arrangement, guide pins of the housing specifically match guide ducts in the filter element.
This is to accomplish a mechanical coding which ensures that only a filter element that is suitable or this housing is inserted into the housing.
Furthermore, a filter element has become known through DE 10 2010 044 258 A1, which has at least one guide duct which penetrates or interrupts pleated walls.
By breaking through a pleated wall or a side strip, this removes material of the pleated wall or of the side strip. This can impair the mechanical strength of the pleated wall or of the side strip. A reduction in the mechanical strength of the pleated wall or of the side strip can especially occur in the edge zone of a breakthrough. This applies particularly to bulky and flexible material with fiber content.
The filter element known from DE 10 2005 048 841 B3 is to be centered by the breakthroughs and the guide pins. If a side strip exhibits mechanical instability in the area of a breakthrough, then a breakthrough can no longer adequately perform the function of guiding and/or centering.
Weakening the material of a pleated wall can furthermore result in forming a specified bending point. This can result in that the uniform bending of a flexible filter element is no longer possible during assembly or during installation. Besides, the geometry of a breakthrough can be deformed when the filter element is bent.
A mechanically introduced breakthrough can especially fray on its edge. When breakthroughs are introduced by mechanical means, in particular by punching, residues of the pleated walls will accumulate which can adhere to the filter element or which must be disposed of, which is costly. The adherence of residues can result in complaints/claims.
Another problem during punching or cutting is that certain pleated areas, in particular flanks of pleats, cannot be brought close enough to a punching or cutting device, because it always requires a counter-bracket to support the pleated wall.